Along with an increase in the price of petroleum-based hydrocarbons due to a decrease in the petroleum-based hydrocarbon supply, the development and improvement of industrial microbial systems for production of chemical compounds and fuels has been of increasing interest. Such industrial microbial systems can completely or partially replace the use of petroleum-based hydrocarbons for production of specific chemical compounds.
Through such systems, many chemical compounds, including antibiotics, anti-malarial drugs, high-quality chemical compounds and fuels such as ethanol, are produced.
Despite strong interest in increasing the yield and production of specific chemical products, efforts are required to develop methods for producing desired chemical products from fermentative microbial cells by feasible fermentation processes and converting the chemical compounds into other compounds.
Fermentation broths produced by biological processes contain not only chemical products, but also microorganisms producing the chemical products, and various organic impurities produced by the metabolic activity of such microorganisms. If organic impurities remain in a chemical product separated from a fermentation broth, these impurities will interfere with a subsequent reaction process for converting the chemical product to another compound. For this reason, it is required to remove these organic impurities to the greatest possible extent.
As methods for solving this problem, International Patent Publication No. WO1998-055442 discloses a method of obtaining a chemical product by subjecting a fermentation product to a pretreatment step, a concentration step and a distillation step. U.S. Pat. No. 8,597,918 discloses a method of obtaining a high-purity chemical product by separating a liquid fraction from a fermentation broth, removing water from the liquid fraction, and removing salts from the liquid fraction, followed by distillation. The above-described methods are methods of removing impurities by centrifugation, ultrafiltration, nanofiltration, ion exchange and salt removal, and thus entail problems in that the impurity removal process consisting of several steps is time-consuming and costly and in that chromatography for ion exchange is difficult to apply to commercial processes and the use of ion exchange resin causes environmental pollution problems.
As a method for solving such problems, Korean Unexamined Patent Application Publication No. 2015-0115533 discloses a method of obtaining a high-purity purified chemical product by subjecting a fermentation broth to a concentration step, a decarbonization step, a pH adjustment and a recovery step using a distillation column. However, this method has problems in that large amounts of acidic solution and basic solution are used which cause environmental pollution and in that metal salts are not efficiently removed.
Accordingly, the present inventors have made extensive efforts to effectively prepare an organic vapor-phase dehydration feedstock from a fermentation broth, and as a result, have found that a gaseous organic vapor-phase dehydration feedstock can be separated from a fermentation broth by direct heating and concentration of the fermentation broth without a separate impurity removal process and can be continuously subjected to a vapor-phase dehydration reaction, thereby completing the present invention.